Dre Campbell Farm
White Spots on Tomato Leaves (Causes & Natural Fix)

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White Spots on Tomato Leaves (Causes & Natural Fixes)

This fruit, often mistaken for a vegetable, is a staple of so many diets, there are dozens of recipes featuring it.

Tomatoes are grown nearly everywhere in the world in gardens or greenhouses. Many experienced gardeners begin their tomato plants from seeds indoors and as they grow, they move them outside to their gardens.

Tomatoes can be grown in two ways: as a bush and as a vine. Like any plant, tomato plants are susceptible to damage with most of this being evident by the appearance of spots and patches on their fruit and leaves.

These blotches are predominantly white and have a variety of textures and sizes. Common causes are insect activity, adverse weather conditions, nutrient deficiencies, and disease.

In this article, we’re going to discuss the different causes, the damage they do, and how to fix them naturally.

It must be noted, in some cases, the damage can’t be fixed. This is due to the extent of it being too much for the plant to survive or to the cause of the damage itself.

Insect Activity

Stink bugs are the main reason for white spots on tomatoes, but there are other insects that also cause this kind of damage such as aphids, thrips, and spider mites.

Leaves sustain the most damage from these pests, and exfoliation is a very real concern. However, infestations can be prevented or dealt with relatively easily.

Treatment:

Prevention:

  • Weed control
  • Companion plants

Adverse Weather Conditions

Sunscald is caused by a plant getting too much sun and/or being in the path of hot, dry wind.

Seedlings that are being moved from indoors to outdoors are the most susceptible to this type of damage. This is also something that can be prevented or treated relatively easily.

Treatment:

  • Removal of damaged leaves

Prevention:

  • Proper transitioning of seedlings
  • Mulch
  • Shade
  • Evening watering
  • Avoiding overhead watering

Nutrient Deficiencies/Surpluses

The kind of soil your tomato plant is put into plays a big part in its health. Issues regarding nutrients are not as common as the first two categories, but it does happen.

The nutrients most affected are:

  • Manganese – best thing for this is transplanting to better soil but fertilizer might also help
  • Nitrogen – the addition of fertilizers such as bat guano can correct this
  • Phosphorus – also treatable with proper fertilizers such as alpha meal
  • Potassium – adding kelp will help with this
  • Calcium – adding lime is one way to increase this nutrient
  • Iron – treated by spraying with molasses or seaweed.

See our complete list of organic fertilizers. 

Disease

This category is the most common cause of white spot damage on tomato leaves.

These are caused by a wide range of conditions including high humidity, poor drainage, poor air circulation, lack of sun, cooler temperatures, and excessive watering.

1. Leaf Spot

Aka Septoria leaf spot first appears on lower leaves, especially on older plants

Treatment: 

  • Use of organic fungicides
  • Handpicking damaged leaves

Prevention: 

  • Crop rotation
  • Leaf debris disposal to keep the disease from overwintering

2. Powdery Mildew

This common disease looks like a thin layer of white powder on leaves

Treatment:

  • Removing the dead leaves
  • Clearing leaf debris
  • Vinegar
  • Neem oil
  • Liquid soap
  • Organic copper fungicides such as Cueva

Prevention:

  • Watering late in the day
  • Improving drainage
  • Providing access to plenty of sunlight

3. Leaf Mold

Mostly affects plants growing inside greenhouses as well as those in high tunnels due to the high humidity and in severe cases, it can also affect the blossoms and fruit.

Treatment:

  • Removing dead leaves
  • Prune where needed
  • Remove leaf debris
  • Application of organic fungicides
  • Cleaning with a commercial sanitizer at end of the growing season

Prevention:

  • Improving air circulation
  • Lowering humidity to below 85%
  • Use resistant plants
  • Use drip irrigation to avoid overhead watering

4. White Rot

Aka white mold — mostly affects plants in wet and cold climates with humidity over 90%.

Treatment:

  • Removing weeds especially pig, ragweed, and wild mustard
  • Remove all infected plants — they can’t be saved

Prevention:

  • Keep weeds out of the garden
  • Rotate crops
  • Avoid planting in any place that has had an outbreak in the last 10 yrs
  • Plant in containers with fresh soil
  • Keep tools clean
  • Provide good drainage
  • Use drip irrigation to avoid overhead watering
  • Sterilize infected soil during summer months using sheeting over the ground and letting the sun raise the temps of the soil to kill spores/mold in it.

5. Mosaic Rot

This is a viral disease that not only diminishes both the yield and the quality of the fruit, it can also kill the plants.

Treatment:

  • Removal of all infected plants — they can’t be saved
  • Boiling tools before washing with a strong detergent to avoid spreading disease
  • Washing hands to avoid spreading disease

Prevention:

See our complete list of tomato diseases (with pictures) and how to treat them. 

Takeaway

These are just a few of the causes of white spots on your tomato plant leaves. Some of them can be devastating to the crop, and the last one, Mosaic Rot, can be spread to other plants as well.

As soon as the blemishes appear, treatment must be done immediately else the entire crop can be devastated.

Even the simple act of handpicking the leaves will help with controlling the damage. Prevention begins with how you set up your garden, the condition of the soil, and adequate drainage.

If starting with seedlings, proper transitioning from indoors to outdoors is of utmost importance.

Despite all the things that can go wrong with tomato plants, they’re actually quite hardy and easy to grow. The effort going into the cultivation and growing of the fruit is well worth the end results.

Sasha Brown

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